Acute pyelonephritis is a common complication of pregnancy and typically necessitates hospital admission. Therapy traditionally consists of inpatient administration of intravenous antibiotics, but recent studies have shown that intramuscular ceftriaxone can be an effective outpatient regimen in selected patients. Wing and colleagues conducted a randomized, two-center trial to compare the effectiveness of intramuscular ceftriaxone with two traditional intravenous antibiotic regimens in the treatment of acute pyelonephritis during pregnancy.

Pregnant women who presented to the emergency department with acute pyelonephritis were eligible for the study if they were at less than 24 weeks' gestation and had no contraindications to the study medication. Patients were randomly assigned to receive one of three drug regimens. The first group received 2 g of ampicillin intravenously every four hours and 1.75 mg per kg of gentamicin intravenously every eight hours following an initial dose of 2 mg per kg. The second group received 1 g of cefazolin intravenously every eight hours. The third group received two 1-g doses of ceftriaxone intramuscularly 24 hours apart, followed by 500 mg of oral cephalexin every six hours. Acetaminophen was administered, and cooling measures were initiated as needed to reduce fever and relieve discomfort. Patients were hospitalized until they were afebrile for 48 hours. On discharge, all patients were given a 10-day course of cephalexin, in a dosage of 500 mg four times daily, followed by 100 mg of nitrofurantoin daily for the remainder of the pregnancy and for six weeks postpartum.

Of the 179 patients enrolled in the study, 62 were given ampicillin-gentamicin, 58 were given cefazolin and 59 were given ceftriaxone. Baseline characteristics were similar in each group. The uropathogen most commonly found was Escherichia coli, present in 76.5 percent of the patients overall. Individual responses to therapy varied widely, but there were no significant differences across the three treatment groups. Patients taking ampicillin-gentamicin were afebrile, on average, after 10 hours, whereas patients in the other two groups were afebrile after 12 hours. The number of days to resolution of costovertebral angle pain and the length of hospital stay were also similar among the three groups. Four patients treated with cefazolin had prolonged fever compared with six patients in each of the other two groups.

Urine cultures were obtained from 149 of the patients two weeks after initial treatment. Four women in the ampicillin-gentamicin group, three women in the cefazolin group and one woman in the ceftriaxone group had positive results for organisms. Ten women had positive cultures later in their antepartum course, and 10 others developed recurrent pyelonephritis. Birth outcomes did not differ across groups. The average birth weight was 3,274 g (7 lb, 3 oz), and 11 (6.9 percent) births were premature.

The authors conclude that the three treatment regimens were equally safe and effective in treating pyelonephritis in pregnancy before 24 weeks' gestation. Significant savings could result from the selective use of ceftriaxone, as it can be administered on an outpatient basis.